Apparatus For Coupling An Energy Storage System To A Variable Energy Supply System

ABSTRACT

A method for coupling an energy storage system to a variable energy supply system includes providing an energy storage system including at least one Vanadium redox battery and at least one battery charge controller. The method also includes electrically coupling the at least one battery charge controller to the variable energy supply system such that the at least one battery is configured to supply a substantially consistent energy output during fluctuating energy loads of the energy supply system.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/247,836, filed Oct. 10, 2005, which is hereby incorporatedby reference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates generally to energy storage systems, and moreparticularly, methods and apparatus for coupling an energy storagesystem to a variable energy supply system.

At least some known wind generation systems produce a fluctuating orintermittent power output due to the variability of wind speed. Whenmultiple generators are electrically coupled together, i.e. inarrangements known as wind farms, the fluctuation in total power outputmay be reduced. Under ideal conditions the variations of power outputwill decrease at a factor of 1 /√n, where n represents the number ofwind generators coupled together. In areas where wind penetration may behigh, coupling a large number of generators generally reduces theoverall power fluctuations on a system wide basis, but may still causepower swing stability concerns. Generally the volatile nature of windgeneration output limits the amount of wind generation that can beconnected to the grid without causing voltage stability problems. Assuch, wind power generation is generally considered a non-firm resourcefor system planning purposes.

It is well known that the demand for electric power fluctuates. Normallypower fluctuations occur on a relatively regular basis. For example, ina typical residential electric power grid, generally demand for electricpower is low at night, peaks during the morning, levels out during theday, and peaks again in the late afternoon. However, there arecircumstances where the demand for electric power suddenly andirregularly increases. From the perspective of an electric power utilitycompany, the associated increase in electric power demand occasionedduring such occasions may be difficult to accommodate because theelectric power demand are generally short lived.

For example, at least some known electric energy storage systems includebanks of electric batteries. Known battery installations are used toprovide electric power in emergency or power-failure circumstances, butgenerally can not be used to provide supplemental power during demandpeaks. For example, known lead-acid batteries are used as standby powersources that may provide emergency lighting and/or standby power sourcesfor telephone exchanges. However, such batteries either do not haveadequate electric energy storage capacity to meet the demands of energystorage systems, or are expensive. To facilitate accommodating shortlived electric power demand increases, at least some known electricpower transmission system are coupled to electric energy storage systemto an so that the energy storage system may be utilized, or turned on,to provide additional electric power during peak demand.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a method for coupling an energy storage system to avariable energy supply system is provided. The method includes providingan energy storage system including at least one Vanadium redox batteryand at least one battery charge controller. The method also includeselectrically coupling the at least one battery charge controller to thevariable energy supply system such that the at least one battery isconfigured to supply a substantially consistent energy output duringfluctuating energy loads of the energy supply system.

In another aspect, a power system for supplying power to a grid isprovided. The system a variable energy supply system and a plurality ofgrid interface units electrically coupled to the variable energy supplysystem via an electrical bus. The system also includes a Vanadium redoxbattery electrical storage system configured to store power from thevariable energy supply system and supply power to the grid.

In a further aspect, an electrical storage system is provided. Thesystem includes a Vanadium redox battery electrical storage system and abattery charge controller in electrical communication with the batteryand a variable energy supply system. The controller is configured todirect electrical power from the variable energy supply system to atleast one of the battery and/or a utility power grid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary wind turbine power system.

FIG. 2 is a schematic view of an exemplary wind turbine power systemincluding an energy storage system.

FIG. 3 is a schematic view of an exemplary embodiment of a multiple windturbine power system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a vanadium-basedreduction/oxidation (redox) regenerative energy storage system thatconverts chemical energy into electrical energy for use with windgeneration systems. While the invention is described and illustrated inthe context of a wind turbine power system, the invention is not limitedto wind turbine power systems. The embodiments set forth herein aretherefore exemplary only and represent various embodiments of theinvention, but are not conclusive of all embodiments. As explainedbelow, these embodiments contribute towards allowing power generatingsystems to store energy, as well as, provide supplemental power to anelectric power grid during demand peaks or store during off-peak times.

FIG. 1 is a schematic of a wind turbine power system 10 including a windturbine generator 12 coupled in electrical communication with a powerutility grid 14. In the exemplary embodiment, wind turbine generator 12provides power to grid 14 via a bus 16 including a grid interface unit18 and a grid interface unit 20. Wind turbine generator 12 also providespower for a critical load 22 coupled in series to bus 16 via a gridinterface unit 24. In the exemplary embodiment, wind turbine generator12 is a 2.7 MW wind turbine generator, bus 16 is a 1100 VDC common DCbus, grid interface device 18 is a 2.7 MW AC/DC inverter, grid interfacedevice 20 is a 3 MVA bidirectional AC/DC, DC/AC inverter, and gridinterface 24 is a 100 KW DC/AC inverter. While system 10 is efficientduring high wind speeds, it is less efficient during fluctuating orintermittent wind speeds and thus power output to grid system 14 variesdue to the variability of the wind speed.

FIG. 2 is a schematic view of an exemplary embodiment wind turbine powersystem 100 including an energy storage system 102. Wind turbine powersystem 100 is substantially similar to wind turbine power system 10,(shown in FIG. 1) and components of wind turbine power system 100 thatare identical to components of wind turbine power system 10 areidentified in FIG. 2 using the same reference numerals used in FIG. 1.

Energy storage system 102 is coupled in electrical communication to bus16 between wind turbine generator 12 and grid interface system 14 via abattery charge controller 104. In the exemplary embodiment, energystorage system 102 is a vanadium redox battery-electrical storage system(VRB-ESS) 102 and controller 14 is a 3 MW DC/DC bidirectional buck/boostconverter.

In the exemplary embodiment, VRB-ESS 102 serves as a buffer betweenvariable supply sources such as wind turbine generator 12 and the firmcompetitive requirements of a power contract such as grid 14. Inalternative embodiments, VRB-ESS 102 adds capacity value to non-firmresources such as wind and Photo-voltaic (PV). One to one response timemakes it capable of charging and discharging over the same duration.VRB-ESS 102 also provides stabilization of wind turbine output and is asource of reactive energy.

VRB-ESS 102 facilitates storing energy in multi megawatt ranges and fordurations of hours or days—from any available input source. The storedenergy can then be provided back to grid interface unit 20 or suppliedto critical load 22 as required and directed. VRB-ESS 102 is configuredto supply steady power in times when the wind is varying, and tocontinue to supply power for a period of time when the wind is gonealtogether.

VRB-ESS 102 is uniquely capable of being charged as quickly as it isdischarged and is able to respond to all forms of power qualityvariations and so can be operated in a UPS mode as well. For loads whichrequire reactive energy, VRB-ESS 102 is fully rated to providevolt-amperes reactive (VARS) at nameplate on a continuous basis eitherwhen charging or discharging. And as such, VRB-ESS 102 is configured tostore bulk power storage in a DC link of a converter in a systemutilizing multiple interleaved insulated gate bipolar transistors (IGBT)converters to convert the battery voltage to AC.

In the exemplary embodiment, controller 104 is configured to facilitatedirecting any extra power from wind turbine generator 12 to chargeVRB-ESS 102, to backup critical load 22, and/or to power grid 14.Controller 104 is also configured to facilitate preventing VRB-ESS 102from over-charging.

FIG. 3 is schematic view of an exemplary embodiment of a multiple windturbine power system 200 including a plurality of wind turbinegenerators 202 coupled in parallel configuration. Wind turbine powersystem 200 is substantially similar to wind turbine power system 100,(shown in FIG. 2) and components of wind turbine power system 200 thatare identical to components of wind turbine power system 100 areidentified in FIG. 3 using the same reference numerals used in FIG. 2.

In the exemplary embodiment, wind turbine generators 202 provide powerto grid 14 via bus 16 including grid interface unit 18 and a gridinterface unit 204. Wind turbine generators 202 also provide power tocritical load 22 via grid interface unit 206. In the exemplaryembodiment, each wind turbine generator 12 is a 2.7 MW wind turbinegenerator, bus 16 is a 1100 VDC common DC bus, grid interface device 18is a 2.7 MW AC/DC inverter, grid interface device 204 is a 9 MVAbidirectional AC/DC, DC/AC inverter, and grid interface 206 is a 300 KWDC/AC inverter. System 200 also includes a VRB-ESS 102 coupled inelectrical communication to bus 16 via a battery charge controller 208.In the exemplary embodiment, controller 208 is a 9 MW DC/DCbidirectional buck/boost converter.

As utilized within the present invention, VRB-ESS 102 facilitatesserving several functions. During power failures, provides power topitch control systems to adjust blade pitch as needed. Furthermore, mostpower systems are also configured with an uninterruptible power system(UPS), VRB-ESS 102 is configured to provide power to the UPS as backuppower to auxiliary loads.

Another advantage of these configurations is the “dynamic braking”energy is handled by the battery storage system. In the exemplaryembodiment, VRB-ESS 102 and controller 104 are configured to absorb theentire wind turbine generator 12 output power for dynamic braking. Thisfunction is ordinarily handled by dissipating the power in largeresistors. VRB-ESS 102 facilitates eliminating these very largeresistors and is more efficient than the resistors.

The above-described invention provides a cost-effective and reliablemethod for coupling an energy storage system to a variable energy supplysystem to be able to facilitate supplying a consistent energy outputduring fluctuating energy demands, storing energy in times of strongwind, and continuing to provide power when the wind speed is low.Positioning a VRB-ESS in a wind turbine power system facilitatesdirecting extra power from a wind turbine generator to store power inthe VRB-ESS, to backup critical loads, and/or to power a utility grid.Furthermore, the VRB-ESS facilitates absorbing output power for dynamicbraking.

Exemplary embodiments of a VRB-ESS are described above in detail. TheVRB-ESS is not limited to the specific embodiments described herein, butrather, components of each system may be utilized independently andseparately from other components described herein. For example, VRB-ESScan also be used in combination with other variable energy supplysystems, and is not limited to practice with only wind generatorturbines as described herein. Rather, the present invention can beimplemented and utilized in connection with many other generators andvariable energy supply systems.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

1-20. (canceled)
 21. A power system for supplying power to a grid, saidsystem comprising: a variable energy supply system; a plurality of gridinterface units electrically coupled to said variable energy supplysystem via an electrical bus; and a Vanadium redox battery electricalstorage system configured to store power from said variable energysupply system and supply power to the grid, wherein said electricalstorage system is configured to absorb an entire power output of saidvariable energy supply system as needed for dynamic breaking within saidvariable energy supply system.
 22. A power system in accordance withclaim 21 wherein said variable energy supply system comprises at leastone wind turbine generator.
 23. A power system in accordance with claim21 wherein said plurality of grid interface units comprise at least oneof an inverter and a converter.
 24. A power system in accordance withclaim 21 wherein said Vanadium redox battery electrical storage systemcomprises a Vanadium redox battery coupled to a battery chargecontroller, and wherein said electrical storage system is configured tosupply a substantially consistent energy output to at least one of thegrid and a critical load when an input to said variable energy supplysystem prevents said variable energy supply system from generating thesubstantially consistent energy output.
 25. A power system in accordancewith claim 24 wherein said battery charge controller is configured todirect excess power from said variable energy supply system to chargesaid Vanadium redox battery, back up the critical load, and power thegrid.
 26. A power system in accordance with claim 24 wherein saidbattery charge controller is configured to direct electrical power to awind turbine pitch control system in the event of a pitch control systemfailure.
 27. A power system in accordance with claim 24 wherein saidbattery charge controller is configured to direct electrical power to anauxiliary load.
 28. An electrical storage system comprising: a Vanadiumredox battery coupled to a variable energy supply system; and a batterycharge controller in electrical communication with said battery and saidvariable energy supply system, said controller configured to directelectrical power from said variable energy supply system to at least oneof said battery and a utility grid, wherein said battery and saidbattery charge controller are configured to absorb an entire poweroutput of said variable energy supply system as needed for dynamicbreaking within said variable energy supply system.
 29. An electricalstorage system in accordance with claim 28 wherein said variable energysupply system comprises at least one wind turbine generator.
 30. Anelectrical storage system in accordance with claim 28 wherein saidbattery charge controller is a bidirectional buck and boost converter.31. An electrical storage system in accordance with claim 28 whereinsaid battery charge controller is configured to direct electrical powerfrom said variable energy supply system to a critical load, said batteryconfigured to supply a substantially consistent energy output to atleast one of the utility grid and the critical load when an input tosaid variable energy supply system prevents said variable energy supplysystem from generating the substantially consistent energy output. 32.An electrical storage system in accordance with claim 28 wherein saidbattery charge controller is configured to direct electrical power to awind turbine pitch control system in the event of a pitch control systemfailure.
 33. An electrical storage system in accordance with claim 28wherein said battery charge controller is configured to directelectrical power to an auxiliary load.
 34. A battery for use in anenergy storage system, said battery configured to be coupled to avariable energy supply system and configured to absorb an entire poweroutput of the variable energy supply system as needed for dynamicbreaking within the variable energy supply system.
 35. A battery inaccordance with claim 34, wherein said battery comprises a Vanadiumredox battery.
 36. A battery in accordance with claim 34, wherein saidbattery is configured to supply a substantially consistent energy outputto at least one of a utility grid and a critical load when an input tothe variable energy supply system prevents the variable energy supplysystem from generating the substantially consistent energy output.
 37. Abattery in accordance with claim 34, wherein said battery is configuredto charge and discharge at the same rate.
 38. A battery in accordancewith claim 34, wherein said battery is configured to be coupled to atleast one wind turbine generator.
 39. A battery in accordance with claim38, wherein said battery is configured to supply electrical power to awind turbine pitch control system of the at least one wind turbinegenerator.
 40. A battery in accordance with claim 34, wherein saidbattery is configured to supply electrical power to an uninterruptiblepower system.